Drying apparatus



July 10, 1923. 1,461,224

' J. w. PEARSON DRYING APPARATUS Filed Dec. 13 1919 4 Sheets-Sheet l .fn VGJJL or.

v fi/ziz 715 660 8022 July 10, 1923. 1,461,224

J. W. PEARSON DRYING APPARATUS Filed Dec. 15, 1919 4 Sheets-Sheet 2 Eavemor.

July 10, 1923. 1,461,224

J. W. PEARSON DRYING APPARATUS Filed D60. 13 1919 4 Sheets-Sheet 5 E N m July 10,1923. 1,461,224

, I J. w. PEARSON DRYING APPARATUS Filed Dec. 13 1919 4 Sheets-Sheet 4 F11 2 l liar e22 tor.

' Patented July 10, 1923.

JOHN W. PEARSON, OF SAN FRANCISCO, CALIFORNIA.

DRYING APPARATUS.

Application filed December 13, 1919. Serial No. 344,689. i

To all whom it may concern:

Be it known that I, JOHN WV. PEARSON, a citizen of the United States, and a resident of the city and county of San Francisco,

State of California, have invented a certain new and useful Drying Apparatus, of which the following is a specification.

The invention relates to apparatus for drying food products, particularly fruits and vegetables.

An object of the invention is to provide a drying apparatus in which all of the heat produced by the combustion of the fuel is available for drying the product.

Another object of the invention is to provide .a drying apparatus of large capacity in which all of the product is continuously subjected to a rapidly moving stream of heated air.

Another object of the invention is to provide a drying apparatus in which complete combustion of the fuel is obtained and the products of combustion are passed in contact with the product.

A further object of the invention is to provide a drying apparatus in which circulation and recirculation of the heated air is controllable.

The invention possesses other advantageous features, some of which with the foregoing, will be set forth at length in the following description, where I shall outline in full that form of the invention which I have selected for illustration in the drawings accompanying and forming part of the present specification. In said drawings I have shown one specific form of drying apparatus of my invention, but it is to be understood that I do not limit myself to such form, since the invention, as expressed in the claims, may be embodied in a plurality of forms. In the drawings I. have shown a two unit drying apparatus consisting of two interconnected units but it is to be understood that the invention may be embodied in a single unit.

Referring to said drawings:

Figure 1 is a horizontal section of a two unit drying. apparatus embodying my invention, part thereof being broken away 'to reduce the size of the figure.

V Figure 2 is a vertical section taken on the line 2-2, Figure 1.

Figure 3 is a vertical cross section 56 through the tunnels.

tunnel or drying chamber.

Figure 4: is a vertical section taken on the Figure 5 is a vertical section on a larger scale through one end of a tunnel. I

Figure 6 is a front elevation of a furnace. Figure 7 is a horizontal section through a furnace taken on the line 7-7, Figure 6.

Figure 8 is a vertical section through a furnacetaken on the line 8-8, Figure 6.

Figure 9 is a vertical section through the furnace taken on the line 9-9, Figure 6.

Figure 10 is a vertical section through the furnace, taken on the line 10-10, Figure 9. Figure 11 is a vertical section through the furnace taken on the line 11-11, Figure 8. The drying apparatus of my invention comprises a furnace, in which fuel, preferably liquid fuel, such as distillate, kerosene or fuel oil is burned to complete combustion. The products of combustion resulting from complete combustion of the fuel are mixed with air and the mixture blown, preferably by a pressure blower, into a long shed or tunnel in which the product to be dried is placed. The product is arranged on trays, which are placed-on cars and the cars are advanced through the tunnel as the drying process progresses and after the tunnel has been fully loaded, the drying process is continuous, the leading car being removed, the cars in the tunnel advanced and a car of undricd product introduced. The moisture absorbing medium, comprising a mixture of air and the products of combustion is introduced into and flows through the tunnel under pressure, so that it always maintains considerable velocity, thereby insuring rapid drying of the product at all parts of the The hot moisture absorbing medium which reaches the far end of the tunnel may be wholly or partly exhausted into the atmosphere or may be returned to the furnace for reheat- .ing and re-entryinto the tunnel when the conditions of operation permit, thereby effecting a saving in heat. The proportion of the hot medium exhausted and recirculated is controllable and may be readily varied in accordance with varying conditions of operation.

By insuring complete combustion of the fuel, the products of combustion do not contain anything which is injurious to the product being dried and may be brought into direct contact with the product without proline 4-4, Figure 1.

ducing any undesirable efiects. Many fuel oils contain sulphur, but the presence of sulphur in the moisture absorbing medium is an advantage in drying fruits and vegetables. By employing the products of com- In the present construction, the furnace or air-heating unit 7 comprises a suitable brick or other heat resistant structure containing two spaced fire-boxes or furnace chambers 2-3. Each furnace chamber is provided with a suitable liquid fuel burner 4: which is preferably disposed on the vertical center line of the chamber. The admission of air into the chamber is controlled by a segmental damper 5 arranged at the front of the chamber.

Means are provided for preventing the flame from being blown away from the burner, a condition which often occurs in oil burners, when the velocity of the air entering the burner becomes excessive or when the feed of oil is reduced, and for preventing the flame from being cooled by the incoming surrounding air, so that complete combustion is assured. Surrounding the burner and extending into the furnace chamber is a cone 5'? of heat resistant material, such as magnesite, the angle of the cone corresponding to the rate of expansion of the burning gases so that the flame contacts with the wall of the cone. Projecting inward from the wall of the cone are fingers or teeth 58 which are rapidly heated to incandescence and which actto immediately reignite the flame in the event that it is blown from the burner. At its larger end the cone is preferably provided with a coarse grating formed of crossed magnesite rods 59 which become incandescent, prevent failure of the flame and break up the cone of the flameas it discharges from the cone 57. An ignitor 81 is preferably arranged in the cone adjacent the burner, for purposes of initial ignition and subsequent ignition necessitated'by failure of fuel supply or other causes. Means are provided within the chamber and intermediate the ends thereof for insuring complete combustion of the liquid fuel. Disposed transversely across the chamber at points remote from the burner 42, are one or more fire-brick checker walls 6, which are spaced apart longitudinally of the chamber. The openings in the successive checker walls are staggered so that the products of com bustion must pass in a tortuous course through the series of checker walls. These checker walls are quickly raised to a very neenaae high temperature by the flame, which is preferably adjusted so that it strikes the front checker wall, and after they have reached the high temperature, the combustion of the fuel passing through them is complete, so that only inert gases pass into the tunnel. I

These checker walls are brought to incandescence by the flame, and not only thoroughly mix the air and flame and insure complete combustion of the fuel, but also act as a heat storage mass, to prevent abrupt changes in temperature in the tunnel. When the checker walls are incandescent, they store a very large amount of heat, so that a brief failure of the fuel supply or a momentary increase in the fuel supply will not materially affect the temperature of the mixture entering the tunnel. Disposed in front of the checker walls 6, and preferably about half way between the front of the furnace chamber and the front checker wall 6, is a checker wall 8, which extends upwardly to about the center of the chamber.

The checker wall 8 should be placed at the apex of the flame discharging from the nozzle in order that it may break up the flame completely and permit the air to gain access to the gases within the cone of the flame. Since it is desirable to vary the size of the flame, the checker wall 8 is preferably movable longitudinally of the furnace, so that it 7 may be positioned at the apex of the flame. For this purpose, the wall 8 is mounted on a carriage 51 provided with legs which extend through slots in the bottom wall of the furnace, and with rollers 52 which travel on rails 53 arranged below the furnace. Rotat ably secured to the carriage is a screw threaded spindle 54 extending to the front of the furnace where it passes through a fixed nut 55. Rotation of the spindle by the hand wheel 56 causes the wall 8 to move longitudinally of the furnace. The checker wall8 catches and causes the consumption of any unburned carbon and breaks up the flame so that air has access to all parts thereof.

Behind the rear checker wall in each furnace chamber, is a chamber 12 having an opening in its upper wall establishing com munication with a superposed chamber 13, extending across and connecting the two furnace chambers, so that the products of combustion from both furnace chambers.

discharge into the chamber 13. Arranged between the two furnace chambers, is an air duct or passage 14, provided on its front end with a damper 15. The air duct passes under the chamber 13 and ,opens into a chamber 16 which extends upwardly to the same height as the chamber 13. The rear wall of the chamber 13 isprovided with a central opening 17, through which the products of combustion pass into the chamber 16 in which they come into contact with the air. The air and the hot products of combustion pass from the chamber 16, through the opening 18 in the rear wall thereof,.into the blower housing 19. The blower is of the pressure type, for example a Sirocco blower and produces the necessary draft in the furnaces and through the air duct and forces the hot moisture absorbing medium into the tunnel. The air and gases of combustion are thoroughly mixed in the blower so that a homogeneous fluid of even temperature throughout is discharged from the blower housing. The blower may be rotated by any suitable prime mover, such as an electric motor driving the belt 21. From the blower housing, the hot mixture passes through the vertically expanded blower throat 22 into the laterally expanding throat 23 and thence into the tunnel in .Which the product is placed. The blower throat 22 is provided with a stack 24 having a damper which is opened when the furnace is started and which remains open while the furnace is warming up, to exhaust the incomplete products of combustion into the atmosphere. When the furnace becomes sufficiently heated to insure complete com-- bustion of the fuel, the damper is closed and the products of combustion are directed into the tunnel.

In the present construction, the tunnel consists of a long frame structure 25, built and lined to reduce heat radiation and conduction to a minimum. The structure is divided into two tunnels 26-27 by the cenevaporator.

ters the tunnel at an angle ,"and the wall, of the throat which extends across the tun-' nel consists of two hinged doors 3233 which may be readily swun back' to permit the passage of a car. 1'. its opposite end the tunnel is provided with a vertically swinging gate 34 which not only closes the end of the tunnel, but causes the moving stream .of moisture absorbing medium to be deflected upward. The gate 34 is pivoted on the shaft 35 and when in its lower position, closing the tunnel, "it lies at an angle to the horizontal, acting to deflect the warm stream of moisture absorbing medium upward into the chamber36. Thewall 37 of the chamber 36 is arched or curved to deflect the moving stream. springing from the side of the chamber 36 is a duct or conduit 38 through which the warm medium The warm medium is thus reheatedand recirculated and this recirculation effects a material saving in heat. In the drawings, the warm medium from one tunnel is conducted to the furnace connected to the other tunnel, since with a two-tunnel plant, such construction is economical, but, where a single tunnel is employed, the warm medium may be conducted back to the furnace of the tunnel.

The blowers employed for forcing the moisture absorbing medium through the tunnel are of the pressure type, so that rapid motion of the medium is assured at all parts of the tunnel. The blowers produce a pressure within the tunnel, which varies with varying circumstances of operation and to relieve this pressure when it increases over a definite maximum, the chamber 36 is provided with a counterweighted door 39, which acts as a valve, to permit the discharge of a portion of the medium into the atmosphere. The door 39 is ordinarily partly open when the apparapasses to the air duct 14 in the furnace.

tus is in operation, permitting the continual discharge of the moisture laden medium, so

that fresh air and gases of combustion may enter the system. At the point where the duct 38enters the duct 14, there is provided a valve or damper 41 which is operable dampers 41 are adjustable to control the amount of humid medium recirculated, to produce the desired condition of humidity in the tunnel. When the dampers are closed, or partly closed, a large volume of warm medium discharges past the gate 39,

and means. are provided for conserving the heat in this discharging medium. -The hot medium'passing the gate '39 enters the chamber 45 which is provided with an air heater '46. The hot medium passes around the pipes of the heater and the air passes through the pipes, and thence through the COIldlllt l? to the furnace.

The rails 31 extend through the tunnel and the tray laden cars move on the rails. Extendin through the tunnel. on opposite sides of t e rails are benches 42 having "side walls 43 and floors 44. These benches fill v the space between the bottom of the car and the bottom of the tunnel, so that no space is left in the tunnel, when the tray laden cars are in the tunnel, for the free passage of the moisture absorbing medium. The medium is therefore constrained to pass between the trays stacked on the cars, so that it is brought into contact with the food product bein which extend across the tunnel are lower than the sides which extend longitudinally of the tunnel, so that a transverse opening dried. The sides of the trays is provided between each two superposed trays and the medium passes through these openingsand over the product on the trays.

.I claim:

1. A drying apparatus comprising an elongated chamber-in which the product to be dried is placed, means for producing a mixture of air and products of complete combustion, means for blowing the mixture into the chamber at one end and a gate at the other end of the chamber arranged to deflect the stream of mixture upwardly and a conduit mediately connected to the other end of the chamber arranged to receive said deflected stream.

2. A drying apparatus, comprising an elongated tunnel in which the product to be dried is placed, a furnace for producing a hot moisture absorbing medium, means for blowing the medium into the tunnel at one end and a second tunnel through which the medium is returned to the furnace from the far end of the first tunnel.

3. A drying apparatus, comprising an elongated tunnel in which the product to be dried is placed, a furnace for producing a hot moisture absorbing medium, means for blowing the medium into the tunnel at one end and a second tunnel parallel to the first tunnel and through which the mediumis returned to the furnace from the far end of the first tunnel.

4. A drying apparatus. comprising an elongated tunnel in which the product to be dried is placed, a furnace for producing a hot moisture absorbing medium, means for blowing the medium into the tunnel atone end and a second tunnel in which products to be dried may be placed and through which the medium is returned to the furnace from the far end of the first tunnel.

5. A drying apparatus, comprising an elongated tunnel in which the product to be dried is placed, a furnace for producing a hot moisture absorbing medium, means for blowing the medium into the tunnel at one end, a second tunnel through which the me dium is returned to the furnace from the far end of the first tunnel and means for blowing the medium through the second tunnel.

6. A drying apparatus, comprising an elongated tunnel in which the product to be dried is placed, a furnace for producing a hot moisture absorbing medium, means for blowing the medium intothe tunnel at one end, a second tunnel through which the medium is returned to the furnace from the far end of the first tunnel and means for reheating the medium after its discharge from the first tunnel. i

7. A drying apparatus, comprising an elongated tunnel in which the product to be dried is placed, a furnace for producing a hot moisture absorbing medium, means for blowing the medium into the tunnel at one end, a second tunnel through which the medium is returned to the furnace from the far end of the first tunnel, means for blowing the medium through the return tunnel and means for reheating the returning medium.

8. A drying apparatus, comprising an elongated tunnel in which the product to be dried is placed, a furnace for producing a hot moisture absorbing medium, means for blowing the medium into the tunnel at one end, a second tunnel through which the me- [dium is returned to the furnace, a conduit connecting the far end of the first tunnel with the far end of the second tunnel and means for heating the medium as it passes through the conduit.

9. A drying apparatus, comprising an elongated tunnel in which the product to be dried is placed, a furnace for producing a hot moisture absorbing medium, means for blowing the medium into the tunnel at one end, a second tunnel through which the medium is returned to the furnace, a conduit connecting the far end of the first tunnel with the far end of the second tunnel, means for heating the medium as it passes through the conduit and means for blowing the heated medium into the second tunnel.

10. A drying apparatus, comprising an elongated tunnel in which the product to be dried is placed, a furnace for producing a hot moisture absorbing'medium, means for blowing the medium into the tunnel at one end, a second tunnel through which the me- 100 dium is returned to the furnace, a conduit connecting the far end of the first tunnel with the far end of the second tunnel, means for heating the medium as it passes through the conduit and means for adding air to the 105 heated medium and blowing the mixture into the second tunnel.

11. A drying apparatus, comprising an elongated tunnel in which the product to be dried is placed, a furnace for producing a 1 4 dried is placed, a furnace for producing a hot moisture absorbing medium, means for blowin the medium into the tunnel at one end, a second tunnel through which a portion of the medium is returned to the furnace from the far end of the first tunnel, a conduit connecting the far ends of the two tunnels, means in said conduit for heating th medium and means for adding air to the medium and blowing the mixture into the second tunnel. lac

13. A drying apparatus, comprising an through the side of the second tunnel at the elongated tunnel in which the product to be far end and a blower for moving the medried is placed, a furnace for producing a dium through saidconduit.

hot moisture absorbing medium, means for In testimony whereof I have hereunto set 5 blowing the medium into the tunnel at one my hand at San Francisco, California, this 15 end, a second tuicilnel thlrl'ough whicl; the me- 10th day of- November, 1919. dium is returne to t e furnace rom the far end of the first tunnel,-a conduit receiv- JOHN PEARSON ing the medium from the far end of the In presence of- 10 first tunnel and delivering it at an angle H. G. Pnos'r. 

